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10 questions from this quiz
n(n+1)2\frac{n(n+1)}{2}2n(n+1)
n(n+1)(2n+1)6\frac{n(n+1)(2n+1)}{6}6n(n+1)(2n+1)
[n(n+1)2]2\left[\frac{n(n+1)}{2}\right]^2[2n(n+1)]2
385385385
363636
225225225
∑r=18r+∑r=18r2\sum_{r=1}^8 r + \sum_{r=1}^8 r^2∑r=18r+∑r=18r2
240240240
2∑r=15r3+3∑r=15r2\sum_{r=1}^{5} r^3 + 3\sum_{r=1}^{5} r2∑r=15r3+3∑r=15r
495495495
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